Method and apparatus for cooling integrated circuit chips using recycled power

ABSTRACT

One embodiment of the present invention provides a system that cools integrated circuit (IC) chips within a computer system. During operation, the system converts heat generated by a heat-generating-device within the computer system into thermoelectric power. The system then supplies the thermoelectric power to an IC chip as a cooling power to reduce the operating temperature of the IC chip, thereby recycling wasted energy within the computer system.

BACKGROUND

1. Field of the Invention

The present invention relates to techniques for improving energyefficiency within computer systems. More specifically, the presentinvention relates to a method and an apparatus that recycles heatdissipated within a computer system and converts the heat into coolingpower for integrated circuit (IC) chips within the same computer system.

2. Related Art

Rapid advances in computing technology presently make it possible toperform trillions of operations each second on data sets as large as atrillion bytes. These advances can be largely attributed to anexponential increase in the density and complexity of integratedcircuits (ICs). Unfortunately, in conjunction with this increase incomputational power, power consumption and heat dissipation of ICs hasalso increased dramatically.

Specifically, high-end computer servers can easily generate 20 kilowattsor more heat. Consequently, some power-demanding system components, suchas a CPU or a graphics processing unit (GPU), can quickly reach unsafeoperating temperatures.

To maintain safe operating temperatures and to prevent overheating forcritical system components, servers typically utilize a number ofcooling techniques. One commonly used cooling technique includesaffixing heat sinks to heat-generating components to thermally conductheat from the components and using powerful fans to increase aircirculation around these components and to pump heat out of the server.Another cooling technique, which is referred to as “thermoelectriccooling” (TEC), uses the Peltier effect to cool an IC chip or to target“hot spots” within the IC chip.

Meanwhile, companies that operate servers are experiencing soaringenergy costs because of the ever-increasing power consumption of theservers. Unfortunately, conventional cooling techniques requireadditional electrical power and therefore increase power consumptionproblems.

One way to reduce both power consumption and heat generation is to uselow-power components. However, this approach may significantly restrictcomputational power and other aspects of server performance.

Hence, what is needed is a method and an system for cooling IC chips inan energy efficient manner without the above described problems.

SUMMARY

One embodiment of the present invention provides a system that coolsintegrated circuit (IC) chips within a computer system. Duringoperation, the system converts heat generated by aheat-generating-device within the computer system into thermoelectricpower. The system then supplies the thermoelectric power to an IC chipas a cooling power to reduce the operating temperature of the IC chip,thereby recycling wasted energy within the computer system.

In a variation on this embodiment, the system converts the heatgenerated by the heat-generating-device into thermoelectric power by:tapping into a temperature difference around the heat-generating-device;and converting the temperature difference into electricity using theSeebeck effect.

In a further variation on this embodiment, the system taps into thetemperature difference around the heat-generating-device by: tappinginto a first temperature reference on the heat-generating-device; andtapping into a second temperature reference from a heat sink, which hasa lower temperature than the heat-generating-device.

In a further variation, the system increases the temperature differenceby reducing the temperature of the second temperature reference.

In a further variation, the system reduces the temperature of the secondtemperature reference by using heat pipes to reduce the temperature.

In a further variation, the system taps into the first temperaturereference by coupling a first thermal interface of a thermoelectricmodule to the heat-generating-device. The system additionally taps intothe second temperature reference by coupling a second thermal interfaceof the thermoelectric module to the heat sink. Consequently, thetemperature difference between the first thermal interface and thesecond thermal interface creates a voltage difference between the twothermal interfaces.

In a further variation, the thermoelectric module can be a bulkthermoelectric device or a thin film thermoelectric device.

In a variation on this embodiment, the system supplies thethermoelectric power to the IC chip as the cooling power by using thePeltier effect. Specifically, the system couples the IC chip to a firstsurface of a thermoelectric cooling module. Next, the system drives thethermoelectric cooling module using the generated thermoelectric power,so that the thermoelectric cooling module actively absorbs heat from theIC chip and releases the heat from a second surface.

In a further variation on this embodiment, the thermoelectric coolingmodule is a thin film thermoelectric element suitable for cooling a hightemperature spot within the second IC chip.

In a variation on this embodiment, the system converts heat generated bya number of heat-generating-devices into thermoelectric power for eachheat-generating-device. The system then combines the thermoelectricpower for each heat-generating-device into an aggregate thermoelectricpower.

In a further variation on this embodiment, the system monitors theoperating temperature of the IC chip using a continuous system telemetryharness (CSTH). Next, the system controls the thermoelectric powersupplied to the IC chip based on the monitored operating temperature byvarying the number of heat-generating-devices used to generate thethermoelectric power.

In a variation on this embodiment, the heat-generating-device caninclude: a microprocessor chip package; a graphics processor chippackage; an ASIC chip package; a video processor chip package; a DSPchip package; a memory chip package; a hard disk drive; a power supply;a graphic card; and any other heat source within the computer system.

In a variation on this embodiment, the IC chip can include: amicroprocessor chip; a graphics processor chip; an ASIC chip; a videoprocessor chip; a DSP chip; and a memory chip.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 provides a block diagram illustrating a computing system inaccordance with an embodiment of the present invention.

FIG. 2A illustrates an exemplary configuration for converting atemperature difference into thermoelectric power in accordance with anembodiment of the present invention.

FIG. 2B illustrates using heat pipes to achieve a low temperaturereference for the thermoelectric power generation in accordance with anembodiment of the present invention.

FIG. 2C illustrates using heat pipes integrated with a heat sink toachieve the low temperature reference in accordance with an embodimentof the present invention.

FIG. 3A illustrates a configuration that uses a TEC to cool an IC chipin accordance with an embodiment of the present invention.

FIG. 3B illustrates using the Peltier diodes as thermoelectric elementsin accordance with an embodiment of the present invention.

FIG. 4 illustrates a technique that integrates a thin film TEC devicewith a chip package to cool hot spots within the chip in accordance withan embodiment of the present invention.

FIG. 5 illustrates the process of provisioning thermoelectric power forcooling a primary chip package in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the invention, and is provided in the context ofa particular application and its requirements. Various modifications tothe disclosed embodiments will be readily apparent to those skilled inthe art, and the general principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the present invention. Thus, the present invention is notlimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the claims.

Overview

As processor speeds continue to increase in modern computer systems, alarge amount of heat is being generated. Some heat sources in computersystems include: the CPU, the GPU, the power supply, and the hard diskdrive (HDD). This heat is generally considered to be waste heat andconsiderable efforts have been taken to effectively remove this heatfrom these heat sources.

One embodiment of the present invention “recycles” the heat dissipatedby electronic devices within a computer system by converting the “wasteheat” into useful electricity. Specifically, the present inventioncouples a thermoelectric device directly to a heat-generating-component(i.e., a heat source) so that the thermoelectric device can convert thetemperature difference into thermoelectric power using the Seebeckeffect.

One embodiment of the present invention then supplies thisthermoelectric power to other parts of the computer system to be used asa cooling power to reduce the operating temperature of otherheat-generating-components. In particular, the thermoelectric power isused in a thermoelectric cooling (TEC) configuration to drive TECdevices. Consequently, some of the “waste energy” within a computersystem is recycled and reused, and furthermore some of the standardcooling power is saved.

Computer System

FIG. 1 provides a block diagram illustrating a computing system 100 inaccordance with an embodiment of the present invention. Computing system100 includes a motherboard 102. Motherboard 102 includes a number of ICchips, such as a processor 104 and a memory chip 106. Processor 104 caninclude any type of processor, including, but not limited to, amicroprocessor (CPU), a digital signal processor, a device controller,or a computational engine within an appliance.

Motherboard 102 additionally includes a graphics processing unit (GPU)108 and a number of chipsets 110-112. In one embodiment of the presentinvention, chipsets 108 and 110 include a northbridge chip and asouthbridge chip, respectively. Motherboard 102 also includes aperipheral bus 114, which couples processor 104, memory 106, GPU 108,and chipsets 110-112 with peripheral devices, such as a storage device116. Note that GPU 108 can alternatively be integrated onto a video cardwhich communicates with motherboard 102 through peripheral bus 114.

Storage device 116 can include any type of non-volatile storage devicethat can be coupled to a computer system. This includes, but is notlimited to, magnetic, optical, and magneto-optical storage devices, aswell as storage devices based on flash memory and/or battery-backed upmemory.

Computer system 100 also includes a power supply 118 which provideselectrical power in a form that is suitable for driving components onmotherboard 102 and peripherals such as storage device 116.

Note that each component described above can dissipate a great amount ofheat during normal operation. In particular, processor 104, GPU 108,storage device 116, and power supply 118 can dissipate more heat thanother system components, and therefore are often air cooled withdedicated fans 120-126.

Note that although the present invention is described in the context ofcomputer system 100 illustrated in FIG. 1, the present invention cangenerally operate on any type of electronics that requires coolingduring operation. Hence, the present invention is not limited to thecomputer system 100 illustrated in FIG. 1.

Thermoelectric Power Generation Using the Seebeck Effect

The Peltier effect and the Seebeck effect are collectively referred toas the “thermoelectric effect,” wherein the Peltier effect and theSeebeck effect are reversals of each other. More specifically, thePeltier effect converts electrical power into a temperature differencewhile the Seebeck effect converts thermal (i.e. temperature) gradientsinto electric power, such a voltage or a current.

The Seebeck effect produces an electromotive force (EMF) andconsequently a voltage different in the presence of a temperaturedifference between two dissimilar conductors, such as metals orsemiconductors. When the two conductors are connected in a completeloop, the EMF causes a continuous current to flow in the conductors.Hence, the Seebeck effect effectively converts thermal energy into athermoelectric power. The voltage created is typically of the order ofseveral microvolts per degree difference.

One embodiment of the present invention utilizes the Seebeck effect toconvert temperature differences within a computer system intothermoelectric power in the form of a voltage or a current. FIG. 2Aillustrates an exemplary configuration for converting a temperaturedifference into thermoelectric power in accordance with an embodiment ofthe present invention. As seen in FIG. 2A, a thermoelectric module 202is sandwiched between a high temperature object 204 and a lowtemperature object 206. More specifically, thermoelectric module 202comprises a bottom substrate 208 which makes thermal contact with hightemperature object 204 at a temperature T_(H), and a top substrate 210which makes thermal contact with low temperature object 206 at atemperature T_(L). Thermoelectric module 202 also includes a series ofthermoelectric elements 212 which are disposed between substrate 208 and210 in a manner which facilitates generating thermoelectric power. Inone embodiment, thermoelectric elements 212 are made of semiconductorthermoelectric materials. We describe these thermoelectric elements inmore detail below.

In one embodiment of the present invention, high temperature object 204is a heat-generating component/device within a computer system. Suchheat-generating components/devices can include, but are not limited to:a microprocessor chip package, a graphics processor chip package, anASIC chip package, a video processor chip package, a DSP chip package, amemory chip package, a power supply, a graphics card, a HDD, amotherboard, or any other heat-generating devices within the computersystem, which can be practically tapped into using thermoelectric module202. Note that bottom substrate 208 of thermoelectric module 202 obtainsthe high temperature reference T_(H) from the top surface of heat source204.

In one embodiment of the present invention, low temperature object 206is a heat sink, which is typically a machined metal device with a basefor thermal contact and a group of fins for heat dissipation. The highthermal conductivity of the metal combined with its large surface areacause a rapid transfer of thermal energy to the surrounding environment,which facilitates maintaining a low temperature in the heat sink. Hence,the top substrate 210 of thermoelectric module 202 obtains a lowtemperature reference T_(L) from the bottom surface of heat sink 206.

Thermoelectric module 202 taps into the temperature differenceT_(H)−T_(L) and continuously generates a thermoelectric power. Whiledoing so, the system effectively “recycles” heat dissipated by heatsource 204 into potentially useful electricity. Referring to FIG. 2A,note that no external power is needed to perform such thermoelectricenergy conversion.

In one embodiment, more thermoelectric power can be obtained byincreasing the temperature difference T_(H)−T_(L). This also allows morewaste energy to be recycled. Because T_(H) is typically difficult tocontrol, one can increase the temperature difference by reducing the lowtemperature reference T_(L). One way to reduce T_(L) for heat sink 206is to use a heat sink fan. However, this requires additional power.

Another technique to reduce temperature T_(L) is by using heat pipes.Heat pipes employ an evaporative cooling mechanism to transfer thermalenergy from one end of a pipe to another by the evaporation andcondensation of a working fluid or coolant.

More specifically, a single heat pipe includes a vacuum tight container,a capillary wick structure and a working fluid. Typically, the heat pipeis evacuated and then back-filled with a small quantity of a workingfluid, just enough to saturate the wick. The atmosphere inside the heatpipe is set by an equilibrium condition of liquid and vapour. As heatenters the heat pipe from one end (the evaporating end), thisequilibrium condition is disrupted, and some working fluid evaporates,which increases the vapour pressure at this end of the pipe. This higherpressure vapour travels to the condensing end of the pipe where theslightly lower temperature causes the vapour to condense, and therebyreleases its latent heat absorbed during vaporization. The condensedfluid is then pumped back to the evaporating end by the capillary forcesdeveloped in the wick structure.

This continuous cycle can transfer large quantities of heat with verylow thermal gradients. Note that the heat pipe operation is passive sothat the only driving force of the heat-transfer process is the heatthat is being transferred.

FIG. 2B illustrates using heat pipes to achieve a low temperaturereference for the thermoelectric power generation in accordance with anembodiment of the present invention. In this embodiment, a group of heatpipes 214 replace heat sink 206 in FIG. 2A. Note that the evaporatingends of heat pipes 214 are in direct contact with top substrate 210 andtherefore continuously absorb and transfer heat away to maintain a lowT_(L) at substrate 210.

FIG. 2C illustrates using heat pipes integrated with a heat sink toachieve a low temperature reference for the thermoelectric powergeneration in accordance with an embodiment of the present invention.Note that integrated heat pipes 214 and heat sink 216 take advantage ofboth the heat transfer ability of the heat pipes and the large heatdissipation surface area of the heat sink, which further increases thesystem's ability to achieve a lower T_(L) at substrate 206.

Note that although we describe using a heat sink or heat pipes to obtaina low temperature reference, other techniques can be used to achieve alow temperature reference, which can include, but are not limited to,using a cooling liquid. Furthermore, configurations in FIGS. 2A-2C areintended for illustrative purposes and therefore should not limit otherpossible configurations which can convert waste heat generated byheat-dissipation devices into thermoelectric power.

Note that the above described technique can be simultaneously employedto multiple heat-generating-devices. Thus, multiple heat sources 204 caninclude a subset of the following: the CPU, the GPU, the memory chips,the chipsets, the HHD, and the power supply. Because the sizes andtemperatures of these devices can be quite different, the amount ofthermoelectric power generated from each of theseheat-generating-devices can vary widely. However, the thermoelectricpower from each of these devices can be combined into an aggregatedpower, for example, by merging a number of tributary thermoelectriccurrents into an aggregate current.

This thermoelectric power can be supplied to other devices in the samecomputer system. For example, it can be used to drive a low power chip.In one embodiment of the present invention, this thermoelectric power isused to drive a conventional cooling device within the same computersystem. This cooling device can include, but is not limited to a coolingfan or a thermoelectric cooler (TEC).

Thermoelectric Cooling Using the Recycled Thermoelectric Power

One embodiment of the present invention uses the thermoelectric powergenerated from dissipated heat in a computer system as a cooling powerfor other heat-generating-devices within the same computer system.

In particular, this thermoelectric power can be used to drive a TECdevice coupled to an IC chip. As mentioned earlier, a TEC deviceutilizes the Peltier effect to directly convert electrical power into atemperature difference.

FIG. 3A illustrates a configuration that uses a TEC to cool an IC chipin accordance with an embodiment of the present invention. As seen inFIG. 3A, the cooling power is provided by thermoelectric power source302, which itself is generated using recycled heat energy. Note thatthermoelectric power source 302 can include a DC voltage source or anequivalent DC current source. Thermoelectric power source 302 is coupledto a TEC circuit. This TEC circuit includes TEC device 304 and copperconnections 306 which couple TEC device 304 and power source 302.

The bottom thermal interface of TEC device 304, which can be a ceramicplate, makes thermal contact with a heat source 308, such as aheat-generating CPU chip or a GPU chip. The Peltier effect creates atemperature difference so that the bottom thermal interface becomes the“cold side.” Heat dissipated from heat source 308 is actively absorbedby the cold side of TEC device 304. The heat is then transferred throughTEC device 304 and released by the top thermal interface (can be anotherceramic plate), which is the “hot side” of the temperature difference.

Note that semiconductors, for example, Bismuth Telluride, can be used asa thermoelectric material for creating the Peltier effect. This ispartially because the semiconductor materials can be more convenientlyconfigured to pump heat, and also because designers can control the typeof charge carrier employed within the cooling circuit. Using asemiconductor TEC material, TEC device 304 can be constructed, in itssimplest form, around a single semiconductor “pellet” which is solderedto an electrically-conductive material on each end (for example by usingcopper plates 310). In this “stripped-down” configuration, the seconddissimilar material required for the Peltier effect is the copperconnection paths 306 to thermoelectric power supply 302.

Note that in FIG. 3A, the heat will be moved (or “pumped”) in thedirection of charge carrier movement throughout the circuit (it is thecharge carriers that transfer the heat). In one embodiment, “N-type”semiconductor material is used to fabricate the pellet so that electrons(which have negative charges) are the charge carrier employed to createthe bulk of the Peltier effect. With a DC voltage source connected asshown, electrons will be repelled by the negative pole and attracted bythe positive pole of the supply, which forces electron flow in aclockwise direction (as shown by the arrows in FIG. 3A). As theelectrons flow through the N-type material from the bottom to the top,heat is absorbed at the bottom thermal interface and is activelytransferred to the top thermal interface, where it is released.

In a further embodiment, P-type semiconductor pellets are employed.These P-type pellets are manufactured so that the charge carriers in thematerial have positive charges (referred to as “holes”). These holesenhance the conductivity of the P-type crystalline structure, allowingelectrons to flow more freely through the material when a voltage isapplied. Positively charged carriers are repelled by the positive poleof the DC supply and are attracted to the negative pole, thus holecurrent flows in a direction opposite to that of electron flow. Becauseit is the charge carriers inherent in the material that convey the heatthrough the conductor, using the P-type material results in heat beingdrawn toward the negative pole of the power supply and away from thepositive pole.

FIG. 3B illustrates using the Peltier diodes as thermoelectric elementsin accordance with an embodiment of the present invention.

In this embodiment, the pairs of P/N pellets are arranged so that theyare connected electrically in series, but thermally in parallel. The topand bottom thermal interfaces 310 provide the platform for the pelletsand small conductive plates 312 connect them in series.

When a DC voltage is applied to the module, both the positively andnegatively charged carriers in the pellet array absorb heat energy fromthe bottom thermal interface (i.e. cold side), which is in thermalcontact with heat source 316, and release the heat from the top thermalinterface (i.e. hot side). This allows the bottom thermal interface tostay cold and to continuously absorb heat. Note that top thermalinterface 310 can be attached to a heat sink to more efficiently spreadthe heat.

Note that above described configurations for a TEC device in FIGS. 3Aand 3B are also applicable to thermoelectric module 202 in FIG. 2. Thedifference is that thermoelectric module 202 uses the reverse Peltiereffect to generate power from the temperature difference.

Hot Spot Cooling Using a “Thin Film”-Based TEC

One embodiment of the present invention uses a thin-film-based TECdevice to cool “hot spots” within an IC chip. Note that heat generationand hence temperature distribution within a chip package is typicallynot uniform. Depending on a specific chip design, some smallregions/spots within a chip can have significantly higher temperaturesthan an average chip temperature. These “hot spots” show up as peakswithin a chip temperature profile as a function of chip dimensions, andcan severely deteriorate the chip performance and reduce lifetime. Onthe other hand, reducing the hot spot temperature a few degrees canreduce thermal stress and can thereby enhance long term reliability.

Note that cooling these hot spots typically requires less power thancooling an entire chip. Therefore, it is more effective to focusthermoelectric cooling power to cool these hot spots using smaller TECelements than to apply a bulk TEC device to the entire chip package tocool the whole chip.

One embodiment of the present invention utilizes semiconductor thin filmthermoelectric materials, for example “thin film superlattices” elementsto cool down hot spots on an IC chip. These thin film elements requiremuch less cooling power (i.e. with higher efficiency) than bulkchip-size TECs.

In one embodiment, the required thermoelectric cooling power for thethin film TEC is provided by bulk thermoelectric modules. In a furtherembodiment, the bulk thermoelectric modules comprise conventional bulkthermoelectric material, such as Bi₂Te₃/Sb₂Te₃, and are constructed intosimilar sizes as the heat-generating devices providing the heat energy(as in FIG. 2A).

FIG. 4 illustrates a technique that integrates a thin film TEC devicewith a chip package to cool hot spots within the chip in accordance withan embodiment of the present invention.

In FIG. 4, a primary chip package 400 comprises a chip die 402 whichproduces a hot spot 404 during operation. Hot spot 404 is the targetedheat source which requires cooling. Note that primary chip package 400can include, but is not limited to a microprocessor chip (CPU) package,a graphics processor chip (GPU) package, an ASIC chip package, a videoprocessor chip package, a DSP chip package, and a memory chip package.In a further embodiment, primary chip package 400 is a chip package in asystem that demands significantly higher operating power than most otherchips in the system.

Chip die 402 is encased by a lid 406 which protects chip die 402 fromabove and protects a substrate 408 from below. Chip die 402 makescontact with lid 406 through a first thermal interface material 410,while also making contact with substrate 408 through solder balls 412.Two tiny thin film TEC elements 414 are disposed at the bottom surfaceof lid 406. Alternatively, TEC elements 414 can be fabricated on the topsurface of chip die 402. Although we show two TEC elements 414, thenumber of TEC elements can be generally greater or less than two.

Note that TEC elements 414 are positioned immediately above hot spot404, and are therefore more efficient in cooling hot spot 404. TECelements 414 typically do not require a large amount of electrical powerto operate. In one embodiment, the power required by TEC elements 414 isdetermined by the heat power generated by hot spot 404.

Note that top surface of lid 406 is thermally coupled to heat sink 416through a second thermal interface material 418, wherein heat sink 416continuously releases heat transferred from the hot spot 404 into theenvironment.

In one embodiment of the present invention, electrical power for TECelements 414 is provided by power-generator chip packages 420 and 422,which are configured to convert their own dissipated heat into thedesired electrical power. Chip packages 420 and 422 comprise chip dies424 and 426, which are thermal coupled to bulk (chip-size)thermoelectric devices 428 and 430, respectively. These thermoelectricdevices are used to transform the thermal energy (that would otherwisebe waste heat) to thermoelectric power, which is then supplied toprimary chip package 400 as the hot spot cooling power. Note that inthis embodiment, thermoelectric devices 428 and 430 are much larger thanthin film TEC elements 414. As a result, sufficient electrical power canbe produced by these chips to drive the “thin film” TEC elements insidea single primary chip package. As discussed in a previous section, othernon-chip heat-generating devices, such as a HDD or a video card can alsobe used to generate the thermoelectric cooling power.

Note that although we describe using small thin film TEC elements forhot spot cooling, a chip-sized TEC, either in bulk form or in thin filmform, can also be used to cool a hot spot within a chip, or to cool anentire chip. However, a significantly higher power may be required todrive these chip-sized TECs. Also note that the number ofpower-generator chip packages can be greater or less than two.

Feedback Control and Electrical Current Flow Direction Control

FIG. 5 illustrates the process of provisioning thermoelectric power forcooling a primary chip package in accordance with an embodiment of thepresent invention. As seen in FIG. 5, a number of secondary chippackages 502506 are configured to operate as thermoelectric powergenerators (TEPGs). In one embodiment, chip packages 502-506 are coupledto “bulk” thermoelectric modules to form bulk TEPGs 508-512,respectively. These bulk TEPGs are capable of converting the heatdissipated from chip packages into electrical power within each of theTEPGs. TEPGs 508-512 are coupled to a TEC 514 within a primary chippackage 516 to provide the cooling power to TEC 514. In one embodiment,TEC 514 is a thin film TEC module configured to cool a hot spot withinprimary chip package 516.

In one embodiment of the present invention, the operating temperatures,including an average chip temperature and hot spot temperatures ofprimary chip package 516, are monitored through one or more sensors. Inone embodiment, these sensors are integrated into a Continuous SystemTelemetry Harness (CSTH) which provides continuous digitized temperatureand wattage feedback from the chip package to a power controller 518. Inone embodiment, if the monitored temperature is above a thresholdtemperature, power controller 518 determines that the power supplied toTEC device 514 is not sufficient, and subsequently provisionssupplementary power to the TEC device 514. This supplementary power canbe generated by introducing an additional TEPG into the power supplypath. On the other hand, if the monitored temperature is below a lowthreshold, it is determined that the power supplied to TEC module 514 ismore than sufficient, power controller 518 adjusts the thermoelectricpower by reducing a TEPG from the supply path, wherein this extra powercan be reserved for other primary chip packages which may needadditional cooling power. In a further embodiment, power controller 518can directly measure an aggregated current input into TEC 514 anddetermines if a sufficient cooling power is achieved.

One embodiment of the present invention provides a mechanism to regulatecurrent flow. Because there are multiple TEPGs simultaneously providingpower to a single TEC module, to prevent any conflict of current flowsbetween these TEPGs, diodes can be used to control current flowdirections. These diode placements are shown in FIG. 5. Note that theyare arranged to regulate multiple supply currents so that the currentsflow in the same direction to always add up. Consequently, each TEPGcontributes its own power to the TEC device without conflicting witheach other.

CONCLUSION

The present invention provides a technique to recycle waste thermalenergy dissipated by electronic components within a computer system byconverting the “waste heat” into useful thermoelectric power usingthermoelectric devices. In particular, heat pipes can be used to creategreater temperature difference around the thermoelectric devices,thereby achieving greater thermoelectric-conversion efficiency.

This thermoelectric power can then be supplied to other systemcomponents, thereby reducing overall system power requirements andsaving energy. In particular, this thermoelectric power can be used todrive thin film thermoelectric elements to cool down hot spots withinchip packages. A CSTH feedback control mechanism can be used to adjustthe amount of cooling power by controlling the number of thermoelectricpower generators.

The foregoing descriptions of embodiments of the present invention havebeen presented only for purposes of illustration and description. Theyare not intended to be exhaustive or to limit the present invention tothe forms disclosed. Accordingly, many modifications and variations willbe apparent to practitioners skilled in the art. Additionally, the abovedisclosure is not intended to limit the present invention. The scope ofthe present invention is defined by the appended claims.

1. A method for cooling integrated circuit (IC) chips within a computersystem, comprising: converting heat generated by aheat-generating-device within the computer system during operation ofthe computer system into thermoelectric power; and supplying thethermoelectric power to an IC chip as a cooling power to reduce theoperating temperature of the IC chip, thereby recycling wasted energywithin the computer system.
 2. The method of claim 1, wherein convertingthe heat generated by the heat-generating-device into the thermoelectricpower involves: tapping into a temperature difference around theheat-generating-device; and converting the temperature difference intoelectricity using the Seebeck effect.
 3. The method of claim 2, whereintapping into the temperature difference around theheat-generating-device involves: tapping into a first temperaturereference on the heat-generating-device; and tapping into a secondtemperature reference from a heat sink, which has a lower temperaturethan the heat-generating-device.
 4. The method of claim 3, wherein themethod further comprises increasing the temperature difference byreducing the temperature of the second temperature reference.
 5. Themethod of claim 4, wherein reducing the temperature of the secondtemperature reference involves using heat pipes to reduce thetemperature.
 6. The method of claim 3, wherein tapping into the firsttemperature reference involves coupling a first thermal interface of athermoelectric module to the heat-generating-device; and wherein tappinginto the second temperature reference involves coupling a second thermalinterface of the thermoelectric module to the heat sink; and wherein thetemperature difference between the first thermal interface and thesecond thermal interface creates a voltage difference between the firstand second thermal interfaces.
 7. The method of claim 6, wherein thethermoelectric module can be a bulk thermoelectric device or a thin filmthermoelectric device.
 8. The method of claim 1, wherein supplying thethermoelectric power to the IC chip as the cooling power involves usingthe Peltier effect, which involves: coupling the IC chip to a firstsurface of a thermoelectric cooling module; and driving thethermoelectric cooling module using the generated thermoelectric power,so that the thermoelectric cooling module actively absorbs heat from theIC chip and releases the heat from a second surface.
 9. The method ofclaim 8, wherein the thermoelectric cooling module is a thin filmthermoelectric element suitable for cooling a high temperature spotwithin the second IC chip.
 10. The method of claim 1, furthercomprising: converting heat generated by a number ofheat-generating-devices into thermoelectric power for eachheat-generating-device; and combining the thermoelectric power for eachheat-generating-device into an aggregate thermoelectric power.
 11. Themethod of claim 10, wherein the method further comprises: monitoring theoperating temperature of the IC chip using a continuous system telemetryharness (CSTH); and controlling the thermoelectric power supplied to theIC chip based on the monitored operating temperature by varying thenumber of heat-generating-devices used to generate the thermoelectricpower.
 12. The method of claim 1, wherein the heat-generating-device caninclude: a microprocessor chip package; a graphics processor chippackage; an ASIC chip package; a video processor chip package; a DSPchip package; a memory chip package; a hard disk drive; a power supply;a graphic card; and any other heat source within the computer system.13. The method of claim 1, wherein the IC chip can include: amicroprocessor chip; a graphics processor chip; an ASIC chip; a videoprocessor chip; a DSP chip package; and a memory chip.
 14. An apparatusthat cools integrated circuit (IC) chips within a computer system,comprising: an energy-conversion mechanism configured to convert heatgenerated by a heat-generating-device within the computer system duringoperation of the computer system into thermoelectric power; and apower-supplying mechanism configured to supply the thermoelectric powerto an IC chip as a cooling power to reduce the operating temperature ofthe IC chip, thereby recycling wasted energy within the computer system.15. The apparatus of claim 14, wherein the energy-conversion mechanismis configured to: tap into a temperature difference around theheat-generating-device; and convert the temperature difference intoelectricity using the Seebeck effect.
 16. The apparatus of claim 15,wherein while tapping into the temperature difference around theheat-generating-device, the energy-conversion mechanism is furtherconfigured to: tap into a first temperature reference on theheat-generating-device; and tap into a second temperature reference froma heat sink, which has a lower temperature than theheat-generating-device.
 17. The apparatus of claim 16, wherein theenergy-conversion mechanism is configured to increase the temperaturedifference by reducing the temperature of the second temperaturereference.
 18. The apparatus of claim 17, wherein the energy-conversionmechanism is configured to reduce the temperature of the secondtemperature reference by using heat pipes to reduce the temperature. 19.The apparatus of claim 16, wherein the energy-conversion mechanism isconfigured to: tap into the first temperature reference by coupling afirst thermal interface of a thermoelectric module to theheat-generating-device; and tap into the second temperature reference bycoupling a second thermal interface of the thermoelectric module to theheat sink; and wherein the temperature difference between the firstthermal interface and the second thermal interface creates a voltagedifference between the first and second thermal interfaces.
 20. Theapparatus of claim 19, wherein the thermoelectric module can be a bulkthermoelectric device or a thin film thermoelectric device.
 21. Theapparatus of claim 14, wherein the power-supplying mechanism isconfigured to supply the thermoelectric power to the IC chip by usingthe Peltier effect, wherein the power-supplying mechanism furthercomprises: a coupling mechanism configured to couple the IC chip to afirst surface of a thermoelectric cooling module; and a drivingmechanism configured to drive the thermoelectric cooling module usingthe generated thermoelectric power, so that the thermoelectric coolingmodule actively absorbs heat from the IC chip and releases the heat froma second surface.
 22. The apparatus of claim 21, wherein thethermoelectric cooling module is a thin film thermoelectric elementsuitable for cooling a high temperature spot within the second IC chip.23. The apparatus of claim 14, further comprising: a second conversionmechanism configured to convert heat generated by a number ofheat-generating-devices into thermoelectric power for eachheat-generating-device; and a combining mechanism configured to combinethe thermoelectric power for each heat-generating-device into anaggregate thermoelectric power.
 24. The apparatus of claim 23, furthercomprising: a monitoring mechanism configured to monitor the operatingtemperature of the IC chip using a continuous system telemetry harness(CSTH); and a controlling mechanism configured to control thethermoelectric power supplied to the IC chip based on the monitoredoperating temperature by varying the number of heat-generating-devicesused to generate the thermoelectric power.
 25. The apparatus of claim14, wherein the heat-generating-device can include: a microprocessorchip package; a graphics processor chip package; an ASIC chip package; avideo processor chip package; a DSP chip package; a memory chip package;a hard disk drive; a power supply; a graphic card; and any other heatsource within the computer system.
 26. The apparatus of claim 14,wherein the IC chip can include: a microprocessor chip; a graphicsprocessor chip; an ASIC chip; a video processor chip; a DSP chippackage; and a memory chip.